Electric primary cell



A ug, 4, 1936. c. J. GORDON ELECTRIC PRIMARY CELL ,filed sept. 25, 1935 v n Patented Aug. 4, 17936 UNITED STATES PATENT OFFICE A Application September 25, 1935, Serial No. 42,039 In Great Britain April 6, 1933 1 claim. (cl. 13s-loo) The object of this invention is to provide an improved primary cell of the kind in which magnesium is the electropositive electrode. Within the term magnesium, it is intended to include appropriate alloys in which magnesium is the predominating material. For such alloys to be suitable, it is necessary that the metals added to the magnesium should not be placed very far away from magnesium in the electro--A chemical series. As an example of an alloy which is appropriate, one containing about 7% of aluminium and from 1-2% of manganese and the remainder magnesium may be mentioned. 'I'he addition of aluminium within the range of 2-7% has been found to be an improvement on commercially pure magnesium. Where the word magnesium is used in the following specification and claim (unless the context indicates otherwise), it is to be assumed that it includes suitable alloys as well as substantially pure magnesium.

The invention relates to primary cells having a layer of fibrous material lying between and in -contact with the magnesium electrode and the second electrode and serving as a carrier for the electrolyte. Suitable cells form the subject of my co-pending application Serial No. 718,769 led 3rd April, 1934, of which this application is a continuation-in-part, and of my co'pending application, Serial No. 42,038` filed September 25, 1935. In such cells to which the invention is applied, the fibrous layer is also made to serve as a means of bringing about depolarization by the action of n air. The layer for this purpose, is placed in contact with air to an appropriate extent and the air is caused by the action of the layer .toellect the depolarization. The full theory of this action is not understood butit appears evident that it is the oxygen in the air which is essential for the depolarizing and that it can be conveyed along the layer to the place where depolarization occurs.

For the brous layer, it is preferable to use a material of open texture. Many fibres are suitable but have somewhat varying degreesv of eiectiveness. It is preferred to use cellulose libres, such as wood wool or blotting paper. This material is inert and readily obtainable and has been found to be particularly effective for the purposes in View.

The present invention is concerned with the electrolyte material used in cells of the kind described.

It appears that, in this type of cell, it is the4 reaction between the water and the magnesium which provides the E. M. F. of the cell. The electrolyte material serves the purpose of providing a conductive path between the electrodes but it has been found that the electrolyte material has an important influence on the working of the cell. 5 It appears that with certain materials the depolarizing action proceeds much more effectively than with others. These are potassium iodide and potassium bromide and they can be used with impervious electrodes or with pervious elec- 10 trodes.

One. form of construction of primary cell to which the present invention is applicable, is illustrated by way of example, in the accompanying drawing, wherein: 15

Figure 1 is a sectional elevation, and

Figure 2, a plan view.

'Ihe type of cell illustrated is intended for a lcomparatively small current, for instance the current may be of the order of 20 milliamperes. The 20 surface of magnesium per ampere is of the orderof square inches (640 square centimetres). 'I'he open circuit voltage is about 1.3 volts.

The magnesium electrode 22 is placed in the centre of the cell and is in the form of a cylin- 25 drical rod with longitudinal flutes on the surface so as to increase the area. It has a terminal screw 23 at the upper end. The centralrod is surrounded by a layer of fibrous material 24 formed by coiling a strip of wood wool into the 30 form of a tube. Outside and inv contact with this layer, is the second electrode 25. This is of porous carbon made in two half cylinders with longitudinal flutes on both the inner and outer surfaces. These two halves are held together by 35 arubber band 46. From the two halves of the electrode 25, connections 26 are taken off and from the terminal screw 23 a connection 21 is taken off. These connections are joined to terminals 28 mounted on the top plate 29 of the cell. The plate 29 and casing 30 are made of insulating material and are connected together by screws 3l. The electrode 25 is spaced from the inner wall of the casing 30 andthe latter has 45 holes 32 to provide that the exterior surface of the carbon electrode 25 is in contact with air.

Near the lower end of the casing is a partition 33 which separates the chamber containing the electrodes from a smallerv chamber 34 in 50 which is placed a pad 35 containing electrolyte material. Communication is provided between the upper and lower chambers by way of an aperture in the partition 33 through which passes fibrous material 36 which is spread out above 55 and below the partition and serves to establish communication between the pad 35 and the fibrous layer 24. The chamber 34 is closed-by a cup 3l which can be removed to receive the pad 35.

When the cell is complete it can be put into action by supplying water to the pad and the brous material. This can readily be done by removing the cup 31, llng with water and replacing it. The brous material 36 is then in contact with the water and feeds it to the layer 24. The cell will now remain active until substantially the Whole of the water has been used up. Each pad of electrolyte material will generally suiiice for several fillings with water and will generally be so designed that it will be exhausted in about the same time as the magnesium used up.

I claim as my invention:-

A primary cell of the kind having its electromotive force generated by the action ot water on magnesium, comprising an electrode formed of magnesium, a second electrode, a layer of brous material of open texture accessible to air lying electrode is ,between and in contact with the electrodes and serving as a carrier for the electrolyte and for air for depolarizing, and an electrolyte material consisting of a solution of a halide formed by the combination of a potassium with a halogen element of atomic weight of 80 and over.

CHRISTIAN JENSEN GORDON. 

